Extended timeframes for testing is frustrating, acknowledges Wilder, but it will inform MDNR and the responsible parties on what the best options are for the future, and help ensure accurate results so that no problem areas go unmarked.

With renewed testing of TCE contamination sites in Camdenton has come worry and residual distrust in government oversight. But looking to ensure a better future is what the additional testing is all about, according to Missouri Superfund Section Chief Valerie Wilder.

The Superfund Section operates under the Missouri Department of Natural Resources (MDNR) and federal Superfund regulations.

In the last couple of years, MDNR has begun new testing for TCE — the industrial solvent trichloroethylene — both at established Superfund sites and newly suspected sites. 

The impetus was a recognition of a gap in data related to relatively new evaluation guidelines from the Environmental Protection Agency. 

Vapor intrusion is now a recognized exposure route to humans for TCE, a “potential human health hazard for noncancer toxicity to the central nervous system, kidney, liver, immune system, male reproductive system, and the developing fetus.” It is “‘carcinogenic to humans’ by all routes of exposure,” according to a toxicological assessment for TCE published by the EPA in September 2011.

The assessment set a chronic inhalation reference concentration for noncancer effects as well as offering guidelines on how the assessment should be used in decision-making for Superfund sites.

The original testing, designation and mitigation or cleanup of the original Superfund sites in Camdenton — 221 Sunset Drive, City Lagoon #3 and Mulberry Well— occurred in the mid-1990s. It should be noted that federal regulations through the Superfund act of 1986 requires any contaminants remaining at these sites be re-evaluated every five years to determine if the remedy is and will continue to be proactive of human health and the environment.

While an agreed-upon timeline for the Camdenton Superfund sites do not exist, it appears these processes helped spur the additional TCE testing in Camdenton.

The main concerns for TCE exposure now lie through both contaminated water and air. Drinking water contamination was documented during the 1990s investigation, resulting in the condemnation of the city’s Mulberry Well. The well was shut off from the city’s drinking water system, but is still pumped to contain the TCE plume contaminating the aquifer in the vicinity of the well. The water that is pumped goes through a stripping process to remove the TCE.

The community and MDNR officials were among those concerned about the gap in data related to vapor intrusion, according to Wilder, and have worked with MDNR and the responsible parties for the sites to renew testing.

TCE levels in indoor air is a direct marker, but sub slab soil gas is also a vapor intrusion indicator, revealing potential for vapors in the soil below and around a structure to infiltrate the building.

With multiple sites and extensive testing required, the new testing has continued for around three years. According to Wilder, sampling is required during each season of the year to make sure the full extent of TCE concentrations is understood. Seasonal variations in temperature and barometric pressure can impact outcomes in vapor testing, she explained.

When the new testing started, it looked first at homes in the Mulberry Drive area of the city due to their proximity to the old manufacturing plant at 221 Sunset Drive. This area is one of three of the old sites where new investigations are occurring.

The Mulberry area homes were tested for indoor air quality, as this is the primary indicator of potential danger for occupants of a building.

Three residential properties are currently undergoing ongoing quarterly monitoring of sub slab and indoor air quality, according to Wilder. Testing is done four times per year to check for TCE amounts above EPA-designated actionable levels. These levels are set based on levels believed to be a danger to human health. If any one of those tests comes back too high, a mitigation system is installed. 

According to Wilder, there are two homes that have had mitigation systems installed. Post-mitigation testing is also done.

Wilder noted that these two homes have two different mitigation systems. The different systems are due to the different styles of construction, one has a crawl space in which a typical subslab depressurization system (similar to radon mitigation) cannot be used so an air purifying unit is utilized instead.

Soil gas testing is also being done around City Lagoon #3, another previously designated Superfund site. This lagoon is also no longer operational, but was contaminated by sewage from the factory at 221 Sunset.

As part of cleanup efforts in the past, sludge was removed from the lagoon and taken to the municipal airport and dumped. New testing has been done on water wells in the area around the airport, and no TCE was found in samples taken there. According to Wilder, it is possible that the TCE, as a volatile organic compound, may have evaporated from the sludge during transport.

However with the decision to close the gap on data related to TCE vapors, vapor wells are being placed around the lagoon to test for TCE in the soil gas. Technicians being close around the lagoon and then expand the field of testing as indicated by test outcomes, according to Wilder. Because of the nature of how the work is done, it is an exploratory sampling to follow the TCE trail, so to speak. 

Sampling started with 20 soil vapor wells around the perimeter of the lagoon, then vapor wells are placed 50 feet out in the directions test results indicate.

Contractors are in the midst of completing that work now. 

Wilder added that the testing is also slowed due to the need to gain access to private property as testing moves beyond the lagoon on city property.

The goal with this testing is to determine if soil gas has migrated and approached any nearby buildings. Residents in the area of the lagoon who might be concerned about the sight of techs in hard hats pulling samples should know that this is investigation and not necessarily a sign that there is a hazard. The work will determine if there is something to worry about. 

If it appears TCE in soil gas migrated to buildings, MDNR will assess vapor intrusion in potentially affected structures. 

In this case, soil gas samples are being pulled fairly quickly due to the mobile lab being used so next steps can be determined very quickly, said Wilder, such as sub slab and indoor air testing.

At this time, actionable TCE levels have not been found within 100 feet of a building.

The outcome of individual testing will determine how long the overall scope of testing will continue, she added. Sampling will continue until TCE levels in the soil gas are no longer seen.

Wilder did estimate that testing could take another couple of weeks, but could be more.

Again, due to the seasonal variations, testing is done quarterly for at least a year.

Because of the recognized past lagoon contamination, it was also recognized that a data gap existed related to the sewer lines of the Sunset Drive facility. 

This contamination source under the defunct plant is the third main subject of current testing.

Soil gas testing beneath the building were recently completed with signs of TCE contamination believed to be related to the sewer lines, and a next phase of investigation is being planned. This testing will be not just soil vapor but actual soil probing. MDNR is also working with former factory workers, who have voluntarily come forward, to find out where the worst of TCE contamination is likely to be, areas where cleaning operations were done and vats of TCE were located. That communication is new and is helping to expedite the process, according to Wilder.

The depth of investigation is to determine specific locations of actionable TCE levels. With the large scale of the building, there may be portions of the building with higher contamination that the rest. 

From specific points of contamination under the old manufacturing facility, the lagoon, Mulberry Well and certain residential areas, all of this testing has an aim. That aim is cleanup and/or mitigation, according to Wilder.

Extended timeframes for testing is frustrating, acknowledges Wilder, but it will inform MDNR and the responsible parties on what the best options are for the future, and help ensure accurate results so that no problem areas go unmarked.

Mitigation systems, similar to those used for radon, are among the more common methods for dealing with TCE contamination. This method is easier in the smaller structure of a residence. Pinpointing contaminated areas within the manufacturing plant are needed to best place systems to remove TCE from the indoor air at the plant.

There are other options though that will be studied at the conclusion of the overall investigation, Wilder said.

Less common, but still a possibility, is treating and cleaning soil as opposed to mitigating vapors. There are also more options for Mulberry Well that could be considered, though it is likely that the current method will remain, according to Wilder.

Final decisions on what will be required for cleanup and mitigation will also be preceded by public hearings. 

The Dawson #2 site on Highway 54, just identified as a contaminated site this year due to a tip from a former factory worker, will also undergo testing and a similar process for a remediation plan. Now under legal negotiations, this site had actionable TCE levels in the sub slab soil, but not in the indoor air of the building on site. This site is an active business. 

Wilder explains that the potential for TCE vapors come into a building above actionable levels can depend quite a bit on the structure, including major cracks in the foundation.

It should be noted that testing is contracted to professional labs and paid for by responsible parties. In these cases, responsible parties include Modine, Hamilton Sundstrand and the City of Camdenton.